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•It has a high water absorption ratio as well as an excellent fire prevention effect.•Analysis of product formation process by reaction.•Raw materials for preparation are cheap.•The ...effects of metal ions on products are discussed in detail.•The preparation technology is simple and feasible.
Coal mine fires pose a threat to the lives of underground workers and cause incalculable losses to the national economy. When a fire occurs, the temperature in the underground wells will rise, which becomes a huge hidden danger that needs to be controlled to prevent disasters. In this paper, using sodium carboxymethyl cellulose as a matrix and through graft copolymerization of acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid, a novel fire-extinguishing gel with high water absorption and high resistance has been prepared. It has a high water absorption ratio as well as an excellent fire prevention effect. The microscopic reaction and structure of the product are analyzed by infrared spectroscopy, thermogravimetry, X-ray diffraction and scanning electron microscopy. By testing the properties of the gel, it is proven that the product has a fast water absorption rate with a high ratio, strong salt tolerance, good water retention and the obvious effects of filling, sealing and fire extinguishing.
•Steel and PP fibers were used individually and in combination at 1.0% fiber content.•Introducing silica fume improved mechanical and durability properties of concrete.•Steel fiber remarkably ...increased splitting tensile and flexural strengths of FRC.•Addition of steel and PP fibers reduced the water absorption of concrete.•Substitution of steel with PP fiber reduced mechanical properties of concrete.
This study investigates the effect of the addition of steel and polypropylene fibers on the mechanical and some durability properties of high-strength concrete (HSC). Hooked-end steel fibers with a 60-mm length were used at four different fiber volume fractions of 0.25%, 0.50%, 0.75%, and 1.0%. Polypropylene fibers with a 12-mm length were used at the content of 0.15%, 0.30%, and 0.45%. Some mixtures were produced with the combination of steel and polypropylene fibers at a total fiber volume fraction of 1.0% by volume of concrete, in order to study the effect of fiber hybridization. All the fiber-reinforced concretes contained 10% silica fume as a cement replacement. The compressive strength, splitting tensile strength, flexural strength, electrical resistivity, and water absorption of the concrete mixes were examined. Results of the experimental study indicate that addition of silica fume improves both mechanical and durability properties of plain concrete. The results also indicate that incorporation of steel and polypropylene fibers improved the mechanical properties of HSC at each volume fraction considered in this study. Furthermore, it was observed that the addition of 1% steel fiber significantly enhanced the splitting tensile strength and flexural strength of concrete. Among different combinations of steel and polypropylene fibers investigated, the best performance was attained by a mixture that contained 0.85% steel and 0.15% polypropylene fiber. Finally, the results show that introducing fibers to concrete resulted in a decrease in water absorption and, depending on the type of fibers, significant or slight reduction in the electrical resistivity of concrete compared to those of the companion plain concrete.
•Super-absorbent polymers (SAPs) is a water-saving material through chemical controlling.•SAPs is stable in the soil and not easily decomposed by bacteria or natural conditions.•The agricultural ...application of super absorbent resin is still in the small-scale experimental demonstration stage.
Super-absorbent polymers (SAPs) are a family of functional polymer material, with a high water absorption function. It absorbs water hundreds to thousands of times heavier than itself and has excellent water retention performance. Once the water absorption expands into a hydrogel, it is difficult to separate the water even under pressure. This article describes the water absorption and retention capacity of polymer water-absorbent resin, a compound that can solve the problem of water shortages in agriculture, which is very important for the development of modern agriculture.
•The absorption in a falling film plate heat exchanger used as absorber is analysed.•Ammonia-water absorption chiller prototype is used to study the absorber behaviour.•A specificity of this work is ...the study of an absorber in real operating conditions.•A one dimension numerical model was developed and experimentally validated.•Mass transfer resistances in both liquid and vapour phases are considered.
In this paper, experimental and numerical studies of heat and mass transfer in a falling film absorber are presented. The investigated absorber is a plate heat exchanger used in a falling film configuration. The ammonia-water solution flows in a falling film mode along the plates. The vapour flows co-current with the falling film and the coolant fluid is in a counter-current flow with the falling film. A prototype of ammonia-water absorption chiller is used to experimentally study the absorber behaviour in real operating conditions. A macro study of the absorber and a local analysis deduced from local temperatures measurements along the falling film are presented. A numerical model and a simulation tool are developed in order to complete the experimental investigations. The associated numerical parametric study aims to separate the coolant mass flow rate impact. The model is validated with experimental data and a maximal relative error of 15% is observed between experimental and numerical results. The results of this study suggest that during the absorption process, mass transfers are controlled by the falling film mass transfer resistance and that the liquid-side heat transfer resistance is negligible.
•Three simplified line-selection methods are proposed. And, compared with the conventional line-selection method, these three simplified methods provide comparable temperature precision, but with a ...much faster selection speed.•Line selection regarding the emerging 2 µm laser sources in absorption thermometry applications is investigated, discussed and evaluated covering a wide temperature range from 400 K to 2000 K.
Line-selection is of vital importance for absorption spectroscopy based thermometry. Up to now, various analytical and numerical line-selection methods have been developed to tackle this issue. Here, concerning the numerical line-selection of water around 2 µm, the conventional method based on the frequency-dependent lower-state energy is simplified through pre-filtering of the candidate absorption lines. As a result, the previous thousands of candidate lines is greatly reduced to a few dozen. With reduced libraries, three simplified line-selection methods are proposed. Line selection results of the simplified methods in the investigated wavelength span from 1800 nm to 1900 nm are discussed and evaluated covering a wide temperature range from 400 K to 2000 K. Comparisons with the conventional method demonstrates that, these three simplified methods provide comparable temperature precision, but with a much faster selection speed.
Chemical vapor deposition of a thin titanium dioxide (TiO2) film on lightweight native nanocellulose aerogels offers a novel type of functional material that shows photoswitching between ...water‐superabsorbent and water‐repellent states. Cellulose nanofibrils (diameters in the range of 5–20 nm) with native crystalline internal structures are topical due to their attractive mechanical properties, and they have become relevant for applications due to the recent progress in the methods of their preparation. Highly porous, nanocellulose aerogels are here first formed by freeze‐drying from the corresponding aqueous gels. Well‐defined, nearly conformal TiO2 coatings with thicknesses of about 7 nm are prepared by chemical vapor deposition on the aerogel skeleton. Weighing shows that such TiO2‐coated aerogel specimens essentially do not absorb water upon immersion, which is also evidenced by a high contact angle for water of 140° on the surface. Upon UV illumination, they absorb water 16 times their own weight and show a vanishing contact angle on the surface, allowing them to be denoted as superabsorbents. Recovery of the original absorption and wetting properties occurs upon storage in the dark. That the cellulose nanofibrils spontaneously aggregate into porous sheets of different length scales during freeze‐drying is relevant: in the water‐repellent state they may stabilize air pockets, as evidenced by a high contact angle, in the superabsorbent state they facilitate rapid water‐spreading into the aerogel cavities by capillary effects. The TiO2‐coated nanocellulose aerogels also show photo‐oxidative decomposition, i.e., photocatalytic activity, which, in combination with the porous structure, is interesting for applications such as water purification. It is expected that the present dynamic, externally controlled, organic/inorganic aerogels will open technically relevant approaches for various applications.
Photoswitching between a water‐superabsorbing state and a water‐repellent state is demonstrated using highly porous, native nanocellulose aerogels coated with a thin TiO2 film by chemical vapor deposition. The nanofibril aggregations and porosity at different length scales are compared to those of similarly treated nanocellulose films and filter paper references.
Abstract
The porosity of concrete is the root cause of durability problems in concrete. Water absorption rate and water absorption speed can be used to detect the pore structure distribution of ...concrete. Based on the principle of permeability coefficient method, the water absorption method was improved in this study. This paper conducted an experimental study on how BA (biomass ash), CMA (cattle manure ash), and FA (fly ash) with different particle sizes affect the water absorption speed and coefficient of concrete. The results showed that among BA, FA, and CMA, the water absorption speed and coefficient of FA are the smallest among all admixtures in concrete, and the water absorption speed and coefficient of BA are the smaller. The water absorption coefficient is greater than that of FA, and the water absorption speed and coefficient of CMA are greater than those of BA. With the same dosage (15% in this test), the smaller the water cement ratio, the smaller the water absorption rate of CMA concrete; The water absorption rate of CMA concrete decreases with the increase of age. When the dosage is the same, the influence of particle size on the water absorption coefficient of concrete is the same as the influence of particle size on the water absorption speed of concrete. Factors affecting the water absorption coefficient of CMA materials include particle size distribution, shape, specific surface area, and so on. The results provide a reference for studying the durability of CMA concrete.
•Mine tailings could substitute silica powder and sand in UHPC.•Characteristics of UHPC were varied by the shape and size of tailings.•Leaching of toxic elements in tailings was highly controlled by ...UHPC matrix.
High production cost and scarcity of raw materials may hinder the application and accessibility of ultra-high performance concrete (UHPC). In the present study, mine tailings, mineral waste products from mining sites, were applied to mitigate these problems. Two types of quartz-based mine tailings produced in South Korea were used to substitute silica powder and silica sand by half and fully in UHPC. The characteristics of UHPC with the tailings, including the compressive strength, workability, water absorption, and leachability of toxic elements, were experimentally evaluated. The effects of the tailings on the characteristics of UHPC varied according to the shape and size of particles of the tailings. The leaching of toxic trace elements from the tailings was highly controlled due to the chemical and physical capsulation of UHPC.
Basalt fiber reinforcement in polymer composites has recently become very competitive to the routinely used synthetic fiber reinforcements. In the present work, composite specimens were prepared with ...basalt fiber mat reinforcement in vinyl ester matrix along with varying quantity of the micro and nano silicon carbide (SiC) filler particle ranging from 1 to 5 wt% in combination. Tribological and water absorption properties of the developed hybrid composites were tested to ascertain its potential for commercial applications. The specimen made of SiC particle addictive combination of 3 wt% nano and 3 wt% micro particle exhibited better mechanical characteristics and this mechanical advantage declines beyond 3 wt% SiC filler addition due to agglomeration and poor dispersion of filler particles in the hybrid composite. The microstructural investigation done via scanning electron microscopy reveals the modes of failure, where better pull‐out resistance was displayed by the fiber bonding characteristics with the filler and vinyl ester matrix up to 3 wt% nano and 3 wt% micro SiC filler content. Similarly, the tribological characteristics of the composite specimen for the optimum filler content specimen were superior in comparison with other combinations. Moreover, the water absorption features of the developed hybrid composites were within the acceptable limits for marine and structural applications.
Four kinds of agricultural wastes (oilseed rape straw (OS), rice straw (RS), wheat straw (WS) and corn stover (CS)) liquefied polyols were used to replace petroleum based polyol and prepare bio-based ...polyurethane (PU) foam successfully. The effect of NCO/OH ratio on PU foaming process and foams properties, such as density, compressive strength, elastic modulus, morphological structure, storage modulus (E’), glass transition temperature (Tg), water absorption ability and chemical structure, was investigated respectively. It is confirmed that CS based polyol appears the highest activity to react with pMDI, while reactivity of OS based polyol is the lowest. Foams made with NCO/OH ratio among 1.4–1.7 appear excellent morphological, physical, mechanical, water absorption and chemical properties, which are comparable with or even better than those of petroleum polyol based PU foams.
•Four kinds of bio-polyols are used to prepare bio-based polyurethane foams.•Effect of NCO/OH ratio on foaming process and foams properties are investigated.•Influence of polyol species and properties on foam performance is discussed.•These bio-based foams show comparable/better property than petroleum based foams.•Confirmed a universally proper NCO/OH ratio range to get excellent bio-based foam.
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